The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In a gasoline engine, over 99% of the engine emissions are converted to clean output (H2O and CO2) by the catalyst in the catalytic converter. However, to operate properly, the catalyst must be heated to a temperature equal to or above a light-off temperature. The light-off temperature is approximately equal to 400° C. The majority of the exhaust gas emissions that are captured exiting the exhaust gas treatment system during an emissions test occur during the first 60 seconds of engine operation while the catalyst temperature is below the light-off temperature, and cannot efficiently convert the engine emissions to H2O and CO2.
Conventional vehicle powertrains typically will execute a Catalyst Light Off (CLO) strategy immediately upon starting the engine when the drivetrain is in park or neutral and hope to finish before the driver depresses the accelerator pedal and drives away. Moreover, conventional vehicle powertrains will typically execute a CLO strategy during conditions when the gasoline engine is operating and when the catalyst is determined to have fallen below the light-off temperature. This way the focus of CLO strategy can be on the emissions performance of the engine and not the drivability of the vehicle.
As a whole, conventional CLO strategies are effective at reducing gas emissions, however there is a need in the art for CLO strategies that further reduce emissions and which improve the diagnostic reproducibility and reliability of catalyst performance while maintaining the driving quality of motor vehicle engines.